A document creating person operates a document creation device to create an electronic document by use of a desired font, and the electronic document is displayed on a document browsing device of a document browsing person. In this case, unless the document browsing device has the same font as that of the document creation device, the document browsing device does not display the electronic document with the font desired by the document creating person.
An example of such an electronic document is an HTML document delivered from a web server to a document browsing device via, for example, a communication line to be browsed as a website.
In order to allow the HTML document to be browsed by the document browsing device as being intended by the document creating person, a font delivery system has been proposed. The font delivery system creates and delivers a subset font, which is a group of fonts corresponding to characters extracted from the HTML document, and thus makes the HTML document browsable by the document browsing device with the font intended by the document creating person.
For example, the document browsing device acquires a URL designation file registered in the HTML document. Then, based on character codes and styles registered in the URL designation file, the document browsing device extracts a character string for each of the styles from the HTML document. The document browsing device also requests a font server to deliver a font that the document browsing device does not own, among the fonts corresponding to the extracted styles.
In response to the request from the document browsing device, the font server creates, based on the fonts and the character codes corresponding to each of the styles, a subset font representing a group of fonts extracted from a plurality of fonts stored thereon and delivers the subset font to the document browsing device.
Upon acquisition of the subset font, the document browsing device displays the characters in the HTML document with fonts of the subset font, not with the fonts that are set by the document browsing device. It is described that in this manner, the HTML document is made browsable as being intended by the document creating person (see Patent Document 1).
In addition, recently, the speed of the communication line is increased and the performance of the document browsing device is improved to shorten the time required to acquire the subset font and display the document with a font of the subset font. Thus, a browsing person is allowed to browse a website with an improved level of design with no stress.
When the above-described website formed with the HTML document and a font of the subset font is browsed, the document browsing device stores the subset font on, for example, a cache folder or the like in order to display the HTML document more efficiently in the future.
This provides an undesirable possibility that a browsing person in bad faith easily replicates a font file like the subset file stored on the document browsing device to illegally use the subset font for a use not intended by the document creating person.